For the Royal Navy World War Two started in 1939 and the senior service quickly discovered anti-aircraft defences were absolutely essential to fend
off the Luftwaffe. DP guns were used for heavy AA, 40mm Pom-Poms for medium AA and Vickers quad .50 MGs for light AA. The USN watched in
interest. The USN had the DP 5-inch/25 guns mounted of the cruisers and older battleships and had developed the dual 5-inch/38 mounts for the fast
battleships being built. For light AA, the .50 water-cooled MG was perfectly suitable. However, a medium AA gun was needed and rather than adopt
the British 40mm Pom-Pom or use an obscure 40mm gun from the Swedish firm of Bofors, an American design was needed. The result was the
quadruple 1.1-inch (28mm) gun mount known unofficially as the Chicago Piano. The ordnance proved to be a flop as it was over-weight, subject to
over-heating and subject to frequent jamming. Eventually the USN discovered that the Swedes knew their business with the Bofors 40mm, a far
superior weapon system. Still  it was the Chicago Piano that was the standard medium AA gun on December 7, 1941 and throughout 1942. Even in
later years of the war some warships retained their 1.1-inch mounts.
3D Model Parts produces a 1:700 scale quadruple Chicago Piano mount in resin,
which is far finer than kit provided plastic parts but clearly more three dimensional than brass photo-etch parts. Eight mounts are included in a tube
with a price of $7.49. Check out the photographs to see the excellent details.